This invention relates primarily to prosthetic devices such as ventilation or drain tubes which are surgically inserted in the eardrum and are useful for equalizing pressure between the middle and outer ears and draining otitus media from the middle ear. More specifically, the invention relates to a ventilation tube which is at least partially biodegradable so that it can be removed without requiring the patient to undergo additional surgery after insertion.
While an exemplary embodiment of the subject invention is illustrated as a ventilation tube, the invention may also be applied to other prosthetic devices which communicate between various portions of the body or between the atmosphere and the body.
With particular reference to the ventilation tube application, the typical remedy for middle ear effusion is a myringotomy surgical procedure, which involves cutting a slit in the eardrum to relieve a buildup or reduction of pressure in the middle ear cavity. A variety of ear ventilation tubes for insertion into such a slit have been introduced over the years in an attempt to keep the eardrum slit open for a sufficient period of time following the surgery to allow pressure to equalize between the middle and the outer ears. Since a slit in the eardrum tends to heal within twenty-four hours, a plastic tube has been used to keep the slit open and allow the equalization of pressure.
Problems have developed when such ventilation tubes have fallen out of the eardrum too soon, which requires surgical insertion of another tube, or when the tube is taken out too late, which exposes the middle ear to possible infection from water or other substances migrating from the outer ear and possible perforation of the eardrum. Such ventilation tubes have also fallen into the middle ear or have had to be removed by additional surgery. Most of the currently used ventilation tubes, if not extruded naturally, are removed and are not intended to be left in the ear permanently.